For volume image reconstruction, an iterative algorithm has been developed by various groups and includes a total variation (TV) minimization iterative reconstruction algorithm. Iterative reconstruction additionally involves Algebraic Reconstruction Technique (ART), Simultaneous Algebraic Reconstruction Technique (SART) or Ordered-subset Simultaneous Algebraic Reconstruction Technique (OS-SART).
Prior art has attempted some use of weights in iterative reconstruction processes. For example, the reconstruction of the image was performed iteratively, wherein the updates were weighted with the intrinsic statistical error of the measured photon counts as disclosed in U.S. Pat. No. 7,526,060. The exemplary weight is the statistical uncertainty of a Poisson distribution. In another example, the reconstruction of the image was performed iteratively, wherein the updates were weighted with a predetermined window weighting function as disclosed in “Correction of Iterative Reconstruction Artifacts in Helical Cone-Beam CT,” by Zeng et al. 10th International Meeting on Fully Three-Dimensional Image Reconstruction in Radiology and Nuclear Medicine P. 242 (2009).
Other prior art techniques include signal to noise ratio (SNR) for weighting during iterative reconstruction. For example, the detector readings are properly weighted with respect to each other according to their SNR based upon a confidence measure that is inversely proportional to an estimate of the SNR of the line integral during ART or SART. “SNR-Weighted ART Applied to Transmission Tomography,” Kohler et al., Nuclear Science Symposium Conference Record, IEEE (2003).
Other prior art techniques yet further include a longitudinal Hamming window in weighing image reconstruction in conjunction with ART or SART algorithms. The length of the window is varied for suppressing noise based upon the number of points describing the part of the ray cut by the reconstruction circle. “Simultaneous Algebraic Reconstruction Technique (SART)” Andersen et al., Ultrasonic Imaging 6, 81-94 (1984).
Despite the above prior art efforts, the noise suppressions and the artifact reductions remain generally separated and conflicting in weighted iterative reconstruction techniques.